A wide variety of devices are available for consumers today. Many of these devices have connectors that that facilitate communication with and/or charging of the corresponding device. These connectors often interface with other connectors on cables that are used to connect devices to one another. Sometimes, connectors are used without a cable to directly connect the device to another device, such as a charging station or a sound system.
As smart-phones, media players, health monitoring devices and other electronic devices become increasingly prevalent, consumers become more reliant on the connectors and cables required to connect these devices to other computing devices and electrical outlets. The devices, and therefore the connectors for the devices and their corresponding cables, remain with consumers throughout the day as they travel in and out of fitness centers, kitchens, offices, factories, automobiles, and many other places.
Many of these locations provide opportunities for exposure to chemicals that pose little or no risk to the consumer, but present a harsh environment for contacts on traditional electrical connectors. For example, connectors regularly come into contact with food, sweat, and other elements that corrode the materials that make up the connector contacts. For example, a cable may even be plugged into an electrical outlet while the connector at the other end is exposed to harsh chemicals, such as a spilled soda, resulting in even greater corrosion.
Contacts are made primarily of copper alloys, due to their advantageous electrical properties. However, copper alloys are also highly susceptible to corrosion. Because of this, contacts are often covered with a sulfumate nickel underplate. As used herein, sulfumate nickel means any nickel that contains at least 98% nickel sulfumate Ni(NH2SO3)2. The nickel underplate acts as a corrosion barrier and a wear barrier, because it is less corrosive and harder than the copper alloy that it covers. A gold layer is often placed on the outer layer in order to decrease contact resistivity. Diffusion of ions between the gold layer and the copper results in additional corrosion. The nickel underplate acts as a diffusion barrier, preventing the diffusion of gold ions from the outer gold layer into the copper alloy and vice versa. But nickel has inherent porosity. The thicker the nickel plating, the more likely pores will be created that can form a channel from the gold layer all the way to the copper alloy. Therefore, porosity defeats the diffusion resistance properties of nickel, because the channels formed between the gold layer and the copper alloy allow for the travel of ions between these layers.
The traditional contacts described above regularly survive industry standard tests for corrosion susceptibility, but these tests are directed to exposure to gases that encourage corrosion, and not the harsher chemicals described above. When consumer electronics and other electronic products are returned because of connector failures, it is common to see corrosion that can only be explained by exposure to food, sweat, or other chemicals that have a corrosive effect on connectors, but fall outside of the industry standard tests. In order to provide connectors that perform well in a typical environment in which consumer electronics are used, protection of the connectors from the chemicals found in these environments is desirable.